Drained peatlands are a characteristic specific to Finnish forestry; almost five million hectares of peatlands have been drained for forestry. Most of that area was drained during the 1960s and 70s, and the stands have already reached the thinning stage. Thinning stands on peatlands are dominated by Scots pine (Pinus sylvestris L.), which is widely used both in wood product and pulp and paper industries in Finland.
The aim of the study was to examine the variation of wood properties of Scots pine in typical thinning stands on peatlands, and to compare the results to those of mineral soil sites. Results concerning top pulpwood from mature peatland pines were used as a reference material. The idea was to get a better understanding about the variation in the wood properties of the pulpwood flow to be able to evaluate the need for pulpwood sorting according to its origin.
The thinning stand material was collected from two sample plots representing site types generally managed for pine. Altogether, eight sample trees were felled. Sample discs were taken at two meter intervals from the stump to the top diameter of 5–7 cm. The properties studied were age, growth rate, basic density, latewood content, heartwood content, moisture content, extractive content and fibre length.
Ring width, basic density and heartwood content varied a lot both within and among the trees in the thinning stands. Trees containing pre-drainage wood showed an extremely high variation in the properties. There are some differences in wood properties between peatland thinning stands and upland first thinning stands. Since the harvesting removals are quite low in peatland thinnings, roundwood sorting within stands is not reasonable. Steering pulpwood stand-wise to different uses might be reasonable. However, this does not eliminate the large variation in certain properties.
Keywords: Scots pine, pulpwood, wood properties, drained peatlands
Authors
Rikala J.
Department of Forest Resource Management, University of Helsinki
Rissanen A.
Department of Forest Resource Management, University of Helsinki
Sipi M.
Department of Forest Resource Management, University of Helsinki
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